THE HISTORY BEHIND A SHANGHAI TOWER | One of the world’s tallest skyscrapers!

Introduction:

The Shanghai Tower is a skyscraper located in Shanghai’s Lujiazui financial district. When it was completed in late-2015, it was the second-tallest building in the world, becoming the third to achieve mega-tall status (over 600 meters). It has won praise for being one of the most sustainably advanced tall buildings in the world and incorporates a number of ‘green’ architectural elements. 

At 632 meters it is China’s tallest building, surpassing Guangzhou’s Canton Tower which was completed in 2010 and stands at 600 meters. Architectural practice Gensler designed the tower to ‘embrace and stimulate the life of the city’. The tower has a curved and twisted form which makes a 120-degree rotation from base to top, the first of its kind in the world. The tower has 123 stories and is divided into nine vertical zones, including: 

 Shops at the base. 

 Offices in the Centre. 

 Hotels in the Centre. 

 Cultural facilities towards the top. 

 An observation deck at the very top. 

It was officially opened in January 2016. In November 2016, the tower won the 2015 Emporia Skyscraper Award. Selected from over 300 buildings of over 100 m in height completed in 2015, the jury was impressed by the Shanghai Tower's 'elegant spiraling cylindrical shape', and the 'extraordinary energy efficiency' provided, in part, by the building's double-skin facade.

Planning and funding 

Planning models for the Lujiazui financial district dating back to 1993 show plans for a close group of three supertall skyscrapers. The first of these, the Jin Mao Tower, was completed in 1999; the adjacent shanghai world financial center (SWFC) opened in 2008. The Shanghai Tower is owned by Yeti Construction and Development, a consortium of state-owned development companies which includes Shanghai Chengtou Corp., Shanghai Lujiazui Finance & Trade Zone Development Co., and Shanghai construction group. Funding for the tower's construction was obtained from shareholders, bank loans, and Shanghai's municipal government. The tower had an estimated construction cost of US$2.4 billion. 

Design and construction: 

The main idea behind Gensler’s design was that the tower provided an alternative to parks spread horizontally across the city. Instead, gathering spaces are stacked vertically, with ‘sky lobbies’ separating the different zones designed, by being naturally-lit plant-filled atriums, to conform to the social environments of town plazas and courtyards. 

To combat Shanghai’s common typhoon-force winds, the tower was designed to have an asymmetrical form, a tapered profile, and rounded corners. After wind tunnel testing, the tower’s form was refined which led to a 24% reduction in structural wind loading when compared to a rectangular building of comparable height. This meant the structure as a whole was lighter and materials savings of $58m were made. 

The unique building shape required more than 20,000 curtain wall panels, with more than 7,000 different shapes. The fabrication of so many individual components would have been unfeasibly complex and costly using traditional computer-aided design tools, but with parametric software and laser measuring technology, a ‘mass customization’ process was possible. 

The tower is built on a 6-meter deep mat foundation that was poured with 61,000 cubic meters of concrete during a continuous 63-hour pour. A strong concrete core and steel super columns support the tower, whilst ‘branches’ extend out at the base of each zone, marking the division of the building into nine cylindrical sections. A 1,000-metric-ton tuned mass damper is positioned near the top of the tower to counteract sway. 

The transparent second skin that wraps the entire building allows maximum daylight while acting as an insulating blanket to conserve energy. This warms up the cool external air in winter and dissipates heat from the interior in summer. The double curtain wall is suspended on massive cantilevered trusses and made stable by the use of hoop rings and struts. As well as the glass skin, the tower’s energy efficiency credentials are boosted by the fact that one-third of the site is green space, by the employment of a trigeneration system (the use of a heat engine to generate electricity, cooling, and useful heat simultaneously), and a grey water/rainwater system. 

The exterior lighting for the tower is powered by 270 wind turbines that are built into the façade. The tower takes the form of nine cylindrical buildings stacked atop each other, totaling 127 floors, all enclosed by the inner layer of the glass façade. Between that and the outer layer, which twists as it rises, nine indoor zones provide public space for visitors. Each of these nine areas has its own atrium, featuring gardens, cafés, restaurants, and retail space, and providing panoramic views of the city. Both layers of the façade are transparent, and retail and event spaces are provided at the tower's base. The transparent façade is a unique design feature, because most buildings have only a single façade using highly reflective glass to reduce heat absorption, but the Shanghai Tower's double layer of glass eliminates the need for either layer to be opaque. The tower is able to accommodate as many as 16,000 people on a daily basis. 

The Shanghai Tower joins the Jin Mao Tower and SWFC to form the world's first adjacent grouping of three supertall buildings. Its 258-room hotel, located between the 84th and 110th floors, is to be operated by Jin Jiang International Hotels as the Shanghai Tower J-Hotel, and at the time of its completion, it will be the highest hotel in the world. The tower will also incorporate a museum. The tower's sub-levels provide parking spaces for 1,800 vehicles. 

Vertical transportation system: 

The vertical transportation system for Shanghai Tower was designed by an American consultant, Edgett Williams Consulting Group with principal Steve Edgett as primary consultant. Working closely with Gensler’s design and technical teams to create a highly efficient core, Edgett created an elevator system in which office floors are served via four sky lobbies each served by double-deck shuttle elevators. Access to the hotel is through a fifth sky lobby at levels 101/102. Each two-level sky lobby serves as a community center for that zone of the building, with such amenities as food and beverage and conference rooms. Local zones are served by single-deck elevators throughout the tower, and the observation deck at the top of the tower is served by three ultra-high speed shuttle elevators which travel at 18 meters per second (40 mph), the highest speed yet employed for commercial building use. These three shuttle elevators are supplemented by three fireman’s elevators which will significantly increase the visitor throughput to the observation deck at peak usage periods. In the event of a fire or other emergency, the building’s shuttle elevators are designed to evacuate occupants from specially-designed refuge floors located at regular intervals throughout the height of the tower. 

In September 2011, Mitsubishi Electric Corp. announced that it had won a bid to construct the Shanghai Tower's elevator system. Mitsubishi supplied all of the tower's 149 elevators (108 of which are lifts), including three high-speed models capable of traveling at 1,080 meters (3,540 ft.) per minute (64.8 kilometers (40.3 mi) per hour). When they were installed (2014), they were the world's fastest single-deck elevators (18 meters/second) and double-deck elevators (10 meters/second). A 10 May 2016 Mitsubishi press release stated that one of the three shuttle elevators had been installed to travel 1230 meters/minute – the equivalent of 73.8 kilometers per hour (46 mph), the highest speed ever attained by a passenger elevator installed in a functioning building. The building also broke the record for the world's furthest-traveling single elevator, at 578.5 meters (1,898 ft.), surpassing the record held by the Burj Khalifa. The Shanghai Tower's tuned mass damper, designed to limit swaying at the top of the structure, was the world's largest at the time of its installation. 

Sustainability: 

The Shanghai Tower incorporates numerous green architectural elements; its owners received certifications from the China Green Building Committee and the U.S. Green Building Council for the building's sustainable design. In 2013, a Gensler spokesman described the tower as "the greenest super high-rise building on earth at this point in time". The building is designed to capture rainwater for internal use and to recycle a portion of its wastewater.

View from Shanghai Tower Observation Deck

The design of the tower's glass façade, which completes a 120° twist as it rises, is intended to reduce wind loads on the building by 24%. This reduced the number of construction materials needed; the Shanghai Tower used 25% less structural steel than a conventional design of a similar height. As a result, the building's constructors saved an estimated US$58 million in material costs. Construction practices were also optimized for sustainability. Though the majority of the tower's energy will be provided by conventional power systems, 200 vertical-axis wind turbines located near the top of the tower are capable of generating up to 350,000 kWh of supplementary electricity per year, and are expected to provide 10% of the building's electrical needs. The double-layered insulating glass façade was designed to reduce the need for indoor air conditioning, and is composed of an advanced reinforced glass with a high tolerance for temperature variations. In addition, the building's heating and cooling systems use geothermal energy sources.

Challenges: 

How do Designers Meet the Challenges? 

 Salient Features

• At present, Shanghai Tower is the tallest building in China and 2nd tallest in the world. 
• The Tower is owned by a consortium of Chinese state-owned companies and designed by American architectural firm Gensler. 
• The construction of the Tower was started in November 2008 and attained its structural height in 2015. 
• It is a super tall building with an architectural height of 632 m and a structural height of 580 m. 
• The building has 128 stories with 5 underground floors. 
• The total floor area includes 380,000 sq. above grade and 170 sq. below grade area. 
• Shanghai Tower is a mixed-use sustainable building with tiered construction. 
• The building has been designed for high energy efficiency which provides multiple separate zones for office, retail, and leisure. The tower had an estimated construction cost of US$2.4 billion.

 

Architectural Features, Challenges, and Design Considerations: 

While designing the Shanghai Tower, the Architects, Gensler kept in mind the traditional lane houses concept of Beijing’s Hutongs and Shanghai’s Shikumen. The neighborhoods have been planned in vertical, each with its own “Sky Garden” to encourage interaction and community sense among the residents. 33 % of site has been reserved for green space as per Shanghai Government’s requirements and the landscape design is done keeping in view Chinese history of nesting temples, towers and places amid gardens.

Exterior view of the tower,                  Section view of the tower,            Atrium view of the tower

The Main Architectural Features of the building are as follows: 

• The tower is designed in the form of 9 cylindrical buildings which are stacked one over the other. 
• The building has twin layers of transparent facade and the outer layer twists through 120 degrees as it rises and the floors are enclosed by the inner layer of the glass facade. 
• Between the inner layer and the outer layer 9 indoor zones are planned which provide public space for visitors and each zone has its own atrium, gardens, retail space, etc. 
• The Japanese firm Mitsubishi Electric had supplied all 106 elevators for the tower which includes 3 high-speed world's fastest elevators with a speed of 18 m/s. Also, these elevators are the farthest-traveling single elevator, at 578.5 meters, surpassing the record held by the Burj Khalifa, the tallest building in the world. 

 Sustainable Design Considerations: 

The Shanghai Tower is designed as one of the most sustainable and advanced tall buildings in the world. The main aspect of its design is the transparent second skin which wraps the entire building. The temperature has been modulated by a ventilated atrium. The mechanical equipment has been planned strategically throughout each zone to provide optimum flexibility and cost efficiency. The tower is the tallest Chinese building and features indoor gardens. It consists of nine gardens on different floors which will be built in the space between the main building and an outer glass curtain wall. The gardens have been divided into nine vertical sections with a height of more than 10 meters each. A public park has also been planned within the building. Shanghai Tower employs several cutting-edge technologies in construction. It is the first building in China to achieve both the LEED Gold certification issued by the US Green Building Council and the China Three-Star Green Building Design Label and is also the highest double-certified green building in the world.

The Main Features of the building are as follows: 

• The Shanghai Tower incorporates a lot of green architecture features and received certifications from the China Green Building Committee and the Green Building Council. 
• The vertical-axis wind turbines have been installed near the top of the tower to generate up to 350,000 kWh of electricity per year. 
• The double-layered insulating glass facade has been designed to reduce the need for indoor air conditioning and is composed of advanced reinforced glass with a high tolerance for shifts in temperature.
• The heating and cooling systems of the building use geothermal energy Further, the gardens nestled within the facade of the building create a thermal buffer zone and improve indoor air quality. 
• Construction practices were optimized for sustainability. Further, the spiraling parapet of the building collects rainwater which is to be used for the HVAC systems.

Structural Challenges Before the Designers 

The designers faced a lot of challenges to make the Shanghai Tower a reality. How? 

 First time ever...... 

• A tower having a weight of 850,000 tons has been built on a soft soil foundation 
• World’s highest wind generators have been installed on the 124th floor (570m high) 

Other challenges before the designers...... 

• Being a super tall building, the Shanghai Tower is slender and flexible and poses challenges to its stability, safety, and performance. 
• A windy climate and active earthquake zone pose difficulties 
• Clay soil at the foundation level makes things further worsen 
• Non-uniform and excessive settlement of the foundation may induce instability during construction. The issue was more critical seeing the clayey strata at the foundation level

The Structural System and Design Considerations to Meet the Challenges 

• The building has been divided into 9 separate zones along its height which are separated by 8 strengthening floors in between.
• The structural system of the Shanghai Tower comprises a core wall inner tube, an outer mega-frame, and six levels of outriggers. 
• The primary lateral resistance of the tower is provided by the central core, outrigger, and super column system which is further supplemented by a mega frame consisting of super columns and diagonal columns along with a double belt truss at each zone. 
• The central core and super columns are composite structures made of steel sections encased by concrete. 
• The central core wall of the tower is not uniform throughout of its height instead it changes as one rises to achieve the economy. 
• The thickness of the core wall varies from 1.2 m at the bottom to 0.5 m at the top of the building. To reduce the thickness and improve its ductility, the central core wall has been designed as a composite shear wall and accordingly, steel plates have been embedded in the flange and web walls of the core tube. 
• The Outer Mega-Frame consists of three parts; 8 Super Columns along with 4 Corner Columns, Radial trusses, and Box Belt Trusses of two-story-high 
• The floors are designed as a composite deck which has profiled steel sheets as the permanent bottom formwork for the reinforced concrete slabs 
• World's largest tuned mass damper has been used to limit sway at the top of the tower 
• The adopted twisting glass facade of the tower reduces wind loads on the building by 24% resulting in a considerable savings in the construction materials. The Tower used 25% less structural steel than a conventional design of a similar height.

Building zone and strengthening floors

The complete structure of the shanghai tower                         Central core of shanghai tower

Outer mega frame system of the shanghai tower

Typical floor system for zone 1-9 of the shanghai tower

Foundation System adopted for the Tower:

• The foundation system for super high-rise buildings generally poses many challenges. 
• To get the required bearing capacity, super-long piles were adopted but to date, the experience with regard to super-long pile foundations is very limited. The design and construction of super-long pile foundations require adequate experience and more sophisticated methods. 
• Super-long bored piles have lengths larger than 50m and a slenderness ratio of more than 50. The load-resisting behavior of super-long bored piles is quite different from those of short and middle-length piles. 
• The construction of super-long bored piles is also complicated and it is very difficult to control the construction quality. 
• Post-grouting techniques were used to reduce the length of the pile thus economy in foundations. 
• The foundation system adopted for the Shanghai Tower is post-grouted bored piles. The tower has been supported on 831 reinforced concrete bore piles. 
• The C50 grade of concrete has been adopted for the piles. 
• A 60-hour continuous concrete pour resulted in to more than 61,000 cubic meters of concrete to create a 6-meter-thick mat foundation. Concrete pouring of such magnitude in a single go breaks the civil construction world record.

 Conclusion: 

Shanghai Tower represents a new vision in super-high-rise building design for the cities of tomorrow. This vision is being realized with the firm support of the Chinese government, which aims to lead the world in promoting sustainable, high-performance building design. In the last decade alone, great examples of these buildings have been designed and constructed in cities across China. Shanghai Tower’s building envelope is one integral part of an overall strategy to achieve these broader sustainable goals. 

The tower’s design process began with a focus on resolving geometric uniqueness and optimizing its performance while balancing aesthetics with production costs, constructability, serviceability, energy efficiency, safety, environmental impact, and other factors. The lengthy and intensive decision-making process involved a broad pool of specialists from Gensler’s design team, its consultants, the client—with its experts and specialty teams, and outside local and government expert panel groups. While producing actual tower drawings for documentation, weekly meetings were held with outside design team reviewers, expert groups, and city and government officials. 

These gatherings would address all issues and forge consensus for the next step in the design process. These meetings were in addition to weekly team coordination meetings that occurred over the course of the past 20 months prior to tendering (at the time of this writing, it was expected that tendering would take place in late March of 2010). In developing numerous options to best address the design goals, I can certainly say that I felt how each day, another step was made toward making this project a global success. Long and critical as it was, perhaps this process will set an example of a process for future super-high-rise building envelope design to which we as professionals, together with our clients, can aspire.